Comparison of different analytic heliospheric magnetic field configurations and their significance for the particle injection at the termination shock

¹ Institut für Theoretische Physik IV, Ruhr Universität Bochum, 44780 Bochum, Germany e-mail: kls@tp4.rub.de
² Unit for Space Physics, North-West University, 2520 Potchefstroom, South Africa

Received: 11 November 2009
Accepted: 19 May 2010

Abstract

Context. Heliospheric magnetic field configurations are relevant on a large scale for the transport of cosmic rays, especially for injecting possibly pre-accelerated particles into the Fermi-I acceleration process of cosmic rays.

Aims. We compare four analytically described fields by calculating the scalar product between their vectors and the corresponding vectors of the Parker spiral field. Because the injection efficiency at the termination shock is highly sensitive to the local inclination of the upstream magnetic fields with respect to the shock normal, we discuss the probability that pick-up ions are injected into the Fermi-I process.

Methods. We extend the previous work comparing different analytically described heliospheric magnetic fields: the Parker and hybrid Fisk field and modifications of both. Because the Fisk-like configurations are only present during periods of low to moderate solar activity, we restrict ourselves to this case by including high-speed streams over the ecliptic and low-speed flow in the latter. In addition, we extend the analysis from an analytic approximation to a numerically computed termination shock surface.

Results. We find that no strong differences in the injection efficiency can be expected for the four field configurations despite significant structural differences inside the termination.

Conclusions. Consequently, the injection efficiency is largely insensitive to the large-scale heliospheric magnetic field configuration.